Pssst. . .the government is trying to control your behavior. Don't grab your tinfoil hat, it's less nefarious than it sounds. Governments often use taxes to change how their citizens behave and promote the greater good. For example, the U.S. government puts a high import tax on steel to encourage the use of U.S.-made steel. Cigarettes are taxed to discourage people from smoking. There's even talk about taxing junk food to nudge people into improving their eating habits and combating obesity.

Those kinds of taxes are used to discourage behavior, but the government can also use taxes to promote behavior. By offering breaks, like tax credits or tax deductions, the government gives people a financial incentive for certain choices. The most famous way the U.S. government does this is by offering tax credits for homeowners. Homeownership is good for the country because it builds wealth and keeps people invested in the places they live. The government encourages homeownership by letting homeowners deduct certain things to save on their taxes, like the interest they've paid on their mortgage.

The government also wouldn't mind if you helped cut pollution and eased the country's dependence on oil. To get you to do that, its offering tax credits on alternate fuel vehicles, or AFVs.

What's an AFV and what will the government do for you if you buy one? Read on to find out.

Tax Credits versus Tax Deductions

When the government really wants to encourage a behavior, they offer a tax credit, not just a deduction. A tax credit is better for consumers than a deduction because a credit reduces the tax a person owes dollar for dollar. A tax deduction only removes a percentage of the tax that is owed.

Alternative Fuel Vehicle Tax Credits

The Honda Civic GX runs on natural gas as well as other alternative fuels.

You've probably noticed that there aren't a lot of cars at your local dealership that run on these fuels. In fact, you're not likely to find any. The Environmental Protection Agency (EPA) lists only one current car model that runs on any of these fuels: the Honda Civic GX [source: EPA].

Still, there are a lot of cars you can buy that will qualify you for tax credits. Though hybrid cars aren't technically AFVs, buying one can still qualify you for some tax breaks. Most major car manufactures offer at least one hybrid model. Though hybrids tend to cost more than gas-only cars, the savings on taxes (and gas) just might be worth it.

But why do hybrids and AFVs earn their drivers tax breaks? Like we mentioned before, the government wants to encourage people to buy them. Vehicles that run on alternative fuel sources cut down on pollution. They also cut down on the amount of oil the country uses, which helps keep prices low and means that we're better able to withstand a catastrophe that interrupts the supply of oil. (Remember when oil refineries were knocked offline after Hurricane Katrina?)

The U.S. government codified the incentives to buy cars that use less oil in the Energy Policy Act of 2005. It covers not only car purchases, but also encourages people to buy more energy-efficient appliances.

All right, enough with the background. On the next page, we'll get to the good stuff. How much money is the government is willing to take off your tax bill, and what you need to do to qualify?

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Local Energy Tax Breaks and How to Find Them

The federal government isn't the only entity that wants you to buy a greener car. State and local governments are in on the game, too. To find out what tax breaks may be in your area, check out your state, county and city's department of finance or taxation's Web site.

What are the Tax Credits?

Under the Energy Policy Act of 2005, the tax credit you get depends on the type of vehicle you buy. But a few rules apply to all hybrids and AFVs:

You must be the original owner of the car. A used car doesn't count.

You must buy the car to use it -- not to resell it. (Otherwise people could just flip cars for the tax credit.)

The car must be used in the U.S.

You need to buy and start using the car between Jan. 1, 2005, and Dec. 31, 2010. (That means that if you bought a hybrid or AFV a while ago and never claimed the credit, you can file an amended tax return and maybe get a refund.)

You need to submit IRS form 8910.

If you buy an AFV and meet the criteria above, you qualify for a $4,000 tax credit [source: EPA]. If you have an AFV that you bought and started using before Jan. 1, 2005, you still may be able to get a $2,000 tax deduction [source: EPA].

Hybrid tax credits and other incentives are a little more difficult to calculate. That's because the government not only wants you to buy hybrids, but also wants to encourage carmakers to produce them. After a company has sold 60,000 hybrid models, the tax credits start to phase out. That means that if you're considering a hybrid, it may pay to go with a carmaker that's new to the hybrid game. Right now the only carmakers that have had the phase-outs begin on their vehicles are Honda and Toyota.

The tax credits for buying a hybrid aren't as great as for AFVs. That's because hybrids still use gas -- they just don't use as much as regular cars. Hybrid tax credits are also based on how fuel-efficient the hybrid is. For example, a two-wheel drive Ford Escape Hybrid gets a larger credit than a four-wheel drive Ford Escape Hybrid because the four-wheel drive system adds weight, which increases the car's gas consumption.

While hybrids that meet the criteria above are eligible for a tax credit of up to $3,400, most aren't efficient enough to qualify for the full amount (the Toyota Prius comes the closest, qualifying for a $3,150 tax credit). What they do qualify for varies by model. The Environmental Protection Agency (EPA) has a list of models that qualify and the amount each qualifies for [source: EPA]. If you bought a hybrid and put it into service before Jan.1, 2005, you can still qualify for a $2,000 tax deduction [source: EPA].

To learn more about AFVs, hybrid cars and different types of taxes, look over the links on the next page.

Cars and... dishwashers?

Energy efficiency doesn't stop with your car. If your fridge is on the fritz, you can replace it with an energy-efficient model and get a tax credit. If you're remodeling, you can also get a credit for using energy-efficient materials. Models and materials that qualify are usually marked at the store, so keep that in mind as you shop.